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G4FAS 174.5 MHz Radio Telescope
( Phase-switched interferometer )

Inspired by a series of articles by John Rainey Smith in the Journal of the British Astronomical Association
1970 August Vol.80 No.5; 1970 October Vol.80 No.6; 1974 August Vol.84 No.5

Illustrative view of Antennae and electronics

Illustrative view
Two ten element Yagi aerials looking skywards set-up on an
east / west base line and spaced about 22 metres apart.
The resulting polar diagram has an equatorial pitch of  4.5 degrees,
which is equivalent to a diurnal motion of 18 minutes / lobe.

Link to a chart recording of Cygnus A
Penned as he whispered through the virtual lobes presented by the pair of spaced antennae.


Electronic modules


A vintage Hameg spectrum analyser served as an ideal receiver
due to its appropriate bandwidth of about 5 MHz.
Oscilloscope to monitor loading of the phase sensitive detector.
Antennae phasing switch ( sq.wave driven ) / Gulton/Rustrak 2" chart-recorder /
L.F. amp;  phase sensitive detector 
(sq.wave driven);  D.C. amp & 1000Hz square wave switch
The lowest unit is an experimental 30 MHz intermediate frequency amplifier.
Not shown are E<->W (20dB/CF439) aerial pre-amplifiers / and other test-instruments /
a stabilised 12 Volt P.S.U. for all solid state modules, including the aerial pre-amplifiers
which receive thier D.C. power via the aerial cables.

Noise bridge @ Noise head

G4COM noise comparator inc noise head
Credit is due to (the late) "Electrovalue" component emporium of Burnage for their
excellent component catalogue; store-keeping and counter service.
Sadly as with many other similar establishments they are long gone.
( How are today's science teachers coping ? )

Most of the hardware including antennae and copies of the relevant BAA journals are offered (for approx. material cost)
to anyone who can convince me they will go to good home.
But first consider the following quotation from an old  B.A.A. "Nature, Aims and Methods" handbook : --
   " - - - anyone capable of building a television set without detailed instructions should (be able to) manage a radio telescope. "